Traveling wave electron discharge device



Nov. 26, 1957 BROCK 'rlmvEL1r-r wAvE- ELEcTRoN DISCHARGE DEVICE Filed Jan. 9, 1953 IN VEN TOR. my uwl/ M/MJ United Stt tent TRAVELING WAVE ELECTRON DISCHARGE DEVICE Lothar Brck, Ulm, Danube, Germany, assigner to Telefunken Gesellschaft fuer drahtlose Tele-graphic G. rn. b. H., Hannover, Germany Application January 9, 1953, Serial N o. 330,373

3 Claims. (Cl. S15- 3.5)

The present invention relates to electron discharge devices and is more particularly concerned with 'the mounting of the electrodes therein.

In certain discharge devices for example transit-held valves of the travelling wave type it is desirable that the axis of the electron gun employed for generating the electron beam should coincide with the axis of the retardation line or helix with a high degree of accuracy since the highest efficiency and greatest amplication iS only obtained when the electron beam is able to lill a maximum cross-section of the helix without actually impinging thereon.

In constructing this type of valve it has become common practice to support the electron gun as a unitary structure directly from current conductors sealed through a glass base and then -seal such glass base to the main body of the envelope previously provided with a suitable retardation line.

With this form of construction however it is diiiicult to arrange that the axis of the electron gun exactly coincides with the axis of the retardation line which sometimes results in a loss of elliciency for the reason given above.

It is therefore an object of the present invention to provide a mounting for electrodes of discharge devices whereby such electrodes may be assembled in a simple manner with a high degree of accuracy of alignment.

According to the invention there is provided an electron discharge device including electrodes constituting an electron gun and a further electrode through which in the operation of the device an electron beam from said gun passes, wherein said electron gun and said further electrode are both mounted from a supporting member which is disposed in a plane transverse to the axes of said electrodes whereby said gun and said further electrode extend therefrom in opposite directions.

In order that the said invention may be more fully understood the construction of a valve of the travelling wave type incorporating the invention will now be described With reference to the single figure of the accompanying drawing. For the sake of clearness only that part of the valve to which the invention relates has been shown since the general construction of valves of this type are well known in the art.

Referring to the drawing a supporting member in the form of a base 1 of glass or ceramic material is provided with a number of metal rod like elements 2 arranged in a circle and sealed through the base 1 in a vacuum tight manner so that they project on opposite sides thereof. The elements 2 which project from one side of the base 1 are cut to a uniform length whereas the parts of the elements which project on the other side are of various lengths three of them being relatively long to support the electron gun as hereinafter referred to. The elements 2 may be sealed through the base 1 so that they are spaced from each other by unequal distances and preferably it is arranged that one of the elements 2 is widely yspaced from ice 2 the other elements. At the center of the base 1 there is arranged a glass tube 3 which forms the housing for the retardation line and together they provide part of the envelope of the valve. The tube 3 is attached to the base 1 in a manner to ensure that it is concentric with the circle of metal elements 2 with its axis parallel with said elements 2 and this can easily be achieved if the 1 and the tube 3 are positioned in the forming operation by means of a jig.

The retardation line is shown in the drawing as a helix 4 but it is to be understood that any other form of retardation line may be used.

The helix 4 is mounted within the glass tube 3 so that it is made co-axial therewith either by allowing the convolutions of the helix 4 to make contact with the internal wall of the tube as illustrated or by mounting the helix 4 so that it contacts a number of angularly spaced insulating strips arranged as spacing members between the helix 4 and the internal wall of the glass tube 3. The end of the helix 4 is connected to the element 2 which is widely spaced from the other element 2 so that it is firmly supported thereby.

The electron gun which comprises an anode 5, a Wehnelt cylinder 6, cathode 7 and its associated heating element 8 is assembled as a unitary structure by means of transverse insulating support members 9, 10 and 11 held spaced apart by three supporting rods 12 only one` of which is shown in the drawing. The insulating members 9 and 10 are of ceramic material and the member 11 is of mica and each of these members are provided with accurately drilled apertures which coincide with the angular spacing of certain of the elements 2. The gun is mounted in position on the base 1 by threading the apertured spacers 9, 10 and 11 over the three elements 2 which have been made of a suicient length for this purpose and the gun is firmly attached thereto by means of eyelets one of which is shown at 13.

Although it is preferred to pre-assemble the gun electrodes in the manner just described it will be understood that the insulating members supporting the electrodes may be assembled directly onto the elements 2 and in this case the rods 12 are not required.

By arranging that the electron gun assembly and the retardation line are both mounted from a common supporting member e. g. base 1, it can be arranged that the electrodes are easily accessible and can be adjusted with respect to each other so that they occupy the positions they are required to take when they are finally enclosed by the envelope of the valve. Furthermore various known methods of precision checking of the assembly can be carried out for instance by passing a parallel ray of light through a hole in the center of the cathode 7 through the electrodes of the gun and the helix 4.

When the electrode assembly has been nally adjusted the envelope of the Valve is completed by means of a tubular bulb portion 14 which is sealed to the base 1 at 15 after which the valve is evacuated and sealed oil:` as indicated at 16. The portion 14 of the envelope may be formed from glass, ceramic or metal, the choice of material depending on the material employed for the base 1.

The construction just described has the advantage over known constructions in that all lthe contacts for the gun electrodes and also the high frequency lead for the helix 4 are provided on a common base 1 which facilitates connecting up the valve in its associated circuits and also simplies the exchanging of valves and the safety precautions that have to be observed in as much as the high potential (LOCO-2,000 volts) connections are all situated away from the point of handling of the envelope.

In special cases, for instance with valves employing high beam currents, it is necessary in order to obtain good focussing, to position an external magnetic eld coil or magnet as close as possible to the electron gun. For valves in which this requirement has to be met it will not be practical to allow the supporting elements 2 to pass through the base 1 to provide conducting leads, and in such instances the elements 2 will be secured to the base 1 on the gun side thereof and serve only for the mounting of the various electrodes; current connections to which Will be made in known manner through the portion of the envelope situated on 'the cathode side of the gun.

Instead of the base l being of glass or ceramic material it vmay be formed of metal. In such instances the elements 2 will be secured to the -metal base and act only for the purpose of accurately positioning the electron gun with respect to the retardation line, current making contacts to the electrodes being provided in a known manner by the use of a glass base arranged on the cathode side of the envelope 14.

In a modification it is possible to dispense with the supporting elements 2 by constructing the electron gun as a unitary structure with the aid of rods 12 and then to mount the assembly by securing the ceramic support 9 to a ,reference surface which is located concentrically and precisely perpendicular to the axis of the helix 4. Such a reference surface lmay be lprovided -by accurately grinding a surface on the metal base or by mounting from said base a suitable member which has been provided with a ground surface on the side thereof which faces the ceramic support 9.

In such an especial form of construction the metallic base 1 can be made completely or in part of a ferromagnetic material, so as iron or covar to get a better magnetical focusing of the electron beam and/ or to shield the .electron gun magnetically in special cases. To get a magnetical shielding of the gun the envelope 14 can be made also lof a ferromagnetical material and can be soldered or welded to the ferromagnetic base i, at the periphery 15 in the Well known way What is claimed as new and desired to be secured by Letters Patent is:

1. In a travelling wave tube electron discharge device, in combination, a tubular structure for enclosing a delay line; a transverse supporting wall at one end of said tubular structure; supporting means mounted on said transverse supporting Wall and extending therefrom in a direction away from said tubular structure; electron gun 4 means arranged on the side of said transverse supporting wall opposite that from which said tubular structure extends and mounted on said supporting means; and a delay line extending into said tubular structure and being mounted independently from said supporting means.

2. In a travelling wave tube electron discharge device, in combination, a tubular structure for enclosing a delay line; a Itransverse supporting wall at one end of said tubular structure; first supporting means mounted on said transverse supporting wall and extending therefrom in a direction away .from said tubular structure; electron gun means arranged on the side of said transverse supporting Wall opposite that from which said tubular structure extends and mounted on said iirst supporting means; second supporting means mounted on -said transverse supporting wall independently from said first supporting means and a delay line extending into said tubular structure and being mounted on -said second supporting means.

3. In a travelling wave tube electron discharge device, in combination, a tubular structure for enclosing a delay line; a transverse supporting wall at one end of -said tubular structure; a plurality of spaced electrically conductive first supporting rods mounted on said transverse supporting Wall and extending therefrom in a direction away from said tubular structure, said first supporting rods having end portions thereof extending through said transverse supporting wall; electron gun means arranged on `the side of -said transverse supporting Wall opposite that from which said tubular structure extends and mounted on said iirst supporting rods; at least one electrically conductive second supporting rod passing through and extending perpendicularly from said supporting wall structure and being spaced from said rst supporting rods and a delay line extending into said tubular structure and making electrical contact with said second supporting rod.

References Cited in the file of this patent UNITED STATES PATENTS 2,524,252 Brown Oct. 3, 1950 2,608,668 I'nes Aug. 26, 1952 2,632,130 Hull Mar. 17, 1953 2,687,490 Rich et al. Aug. 24, 1954 FOREIGN PATENTS 1,023,956 France Jan. 7, 1953 

